The present invention relates to an impulse torque generator for a hydraulic torque wrench, more specifically an impulse torque generator for a hydraulic torque wrench which is highly durable, compact in size and capable of stably generating a large impulse torque.
Conventionally, hydraulic torque wrenches using A hydraulic impulse torque generator with little noise and few vibrations have been developed and put to practical use.
For example, FIG. 6 and FIG. 7 show an example of such hydraulic torque wrench. An impulse torque generator of a hydraulic torque wrench W is realized in a way so as to charge hydraulic oil in a liner chamber La formed in a liner L. A blade insertion groove is provided in a main shaft S inserted coaxially with the liner L and a blade B is inserted in this blade insertion groove. The blade B is put in contact with an inner circumferential face of the liner chamber La by constantly urging it in the outer circumferential direction of the shaft with a spring. A sealed face is formed on the outer circumferential face of the shaft S and the inner circumferential face of the liner chamber La.
It is arranged so that, by turning the liner L with an air motor R, an impulse torque is produced on the main shaft S when the sealed face formed on the inner circumferential face of the liner chamber La, the sealed face formed on the outer circumferential face of the shaft S and the blade B agree with each other.
By the way, in the case of the conventional impulse torque generator for the hydraulic torque wrench W, a construction is adopted in which a blade insertion groove is provided on the shaft S, a blade B is inserted in this blade insertion groove, and this blade B is constantly urged in the outer circumferential direction of the shaft with a spring to be put in contact with the inner circumferential face of the liner L. For that reason, the tip of the blade B comes in sliding contact with the inner circumferential face of the liner L, readily causing wear of the material on both sides and thus presenting a problem in the durability of the system, including breakdown of the spring, etc.
Moreover, another problem was that, because of the necessity of providing a blade insertion groove and a hole in which to insert a spring in the main shaft S, it was necessary to have a large diameter of the main shaft S to maintain the strength of the shaft S, which further increases the size of the equipment itself and complicates the equipment structure.
Furthermore, still another problem was that there was a large energy loss because the operating fluid was liable to leak through the gap between members such as sliding portions, etc., in addition to the sliding resistance between the tip of the blade B and the inner circumferential face of the liner L. Yet another problem was that the temperature of the operating fluid rises with frictional heat produced by sliding, causing fluctuations in the strength of impact torque produced with changes in viscosity of the operating fluid.
In view of the problems of the conventional impulse torque generators for hydraulic torque wrenches, the objective of the present invention is to provide an impulse torque generator for a hydraulic torque wrench which is durable, compact in size and capable of stably generating a large impulse torque by eliminating the blade inserted into the main shaft, which was conventionally essential with this type of impulse torque generator for hydraulic torque wrenches.
To achieve the objective, the impulse torque generator for a hydraulic torque wrench according to the present invention has a main shaft, a cam inserted into the main shaft slidably in an axial direction without turning against the main shaft and forming oil guide holes passing inside it in an axial direction. A cylinder receives the base end of the main shaft and cam, forming oil chambers to be filled with an operating fluid across the cam. Pins are inserted into the cam groove of the cam and provided in a projecting manner on the inner circumferential face of the cylinder. A drive shaft to be connected to the drive source drives the cylinder in a rotating fashion. A check valve shuts off the circulation of the operating fluid between the oil chambers formed across the cam by selectively closing the oil guide holes formed in the cam depending on the relative rotating angle between the cam and cylinder.
This impulse torque generator for a hydraulic torque wrench can slide the cam, in which is inserted the pin, freely in the axial direction without turning against the main shaft, in a state in which the oil guide hole formed in the cam is open, by driving the cylinder with the drive shaft connected to the drive source in a rotating manner. In this state, no impulse torque is produced because there are no restrictions on the cylinder and the cam.
Moreover, as the cylinder is further driven to continue turning, the oil guide hole formed in the cam is closed by the check valve, depending on the relative rotating angle between the cam and cylinder, and the circulation of the operating fluid between the oil chambers formed across the cam is shut off. If, in this state, an attempt is made to slide the cam in the axial direction by further rotated driving of the cylinder, the pressure in the oil chamber placed in the direction in which the cam slides rises, and the pressure in the oil chamber located in the opposite direction drops.
At that time, the pins provided in projection on the inner circumferential face of the cylinder are put in strong contact with the side face on the high-pressure oil chamber side of the cam grooves formed on the outer circumferential face of the cam. Since the sliding of the cam is prevented by shutting off the circulation of the operating fluid between the oil chambers formed across the cam, a large frictional force is produced between the side face of the cam grooves and the pins, restricting the cylinder and the cam. This makes it possible to produce an impulse torque on the main shaft inserted into the cam by transmitting a rotational driving force from the cylinder to the cam through the pins.
Also, this impulse torque generator for a hydraulic torque wrench can improve the system""s durability by eliminating the blade inserted in the main shaft, which was conventionally essential with this type of impulse torque generator for hydraulic torque wrenches, and also because of the absence of any other easily broken parts.
Moreover, since there is no need to provide any blade insertion groove or hole in which to insert the spring in the main shaft, it becomes possible to keep the diameter of the main shaft at the minimum required level and form the system itself in a compact size, and to also simplify the equipment structure, reducing the manufacturing costs of the system.
Furthermore, thanks to the small working resistance of the system and small leakage of operating fluid through the gap between members, there is only a small loss of energy. Because of the reduced temperature increase of the operating fluid due to frictional heat, few fluctuations are produced in the magnitude of the impulse torque produced as a result of changes in the viscosity of the operating fluid. For those reasons, it becomes possible to stably produce a large impulse torque.
Therefore it is possible to form a plurality of cam grooves on the outer circumferential face of the cam and provide, in a projecting manner, a plurality of pins to be inserted in the respective cam grooves so as to have uniform angle intervals. This makes it possible to transmit a rotational driving force from the cylinder to the cam through the pin and produce a more stable impulse torque.
Furthermore, it is also possible for the check valve to close the oil guide hole formed in the cam each time when the cam and cylinder turn 360xc2x0 so as to shut off the circulation of the operating fluid between the oil chambers formed across cam. This makes it possible to produce a large impulse torque by utilizing the inertia of the cylinder each time the cam and cylinder turn by 360xc2x0.
Further, it is possible to form, in the cylinder, an oil guide channel connected between the oil chambers and to provide an output adjusting mechanism for adjusting the magnitude of the impulse torque produced by limiting the flow rate of the operating fluid circulating through the oil guide channel. This makes it possible to easily control the magnitude of the impulse torque produced by limiting the flow rate of the operating fluid circulating through the oil guide channel formed in the cylinder and connecting between the oil chambers.